1. Field of the Invention
The present invention relates to a control method and system, more particularly to a vehicle stability control method and system.
2. Description of the Related Art
Traffic accidents have been a main cause of various losses. To improve road safety, much effort has been put into developing safer, smarter motor vehicles for ensuring safer driving experiences.
The electronic stability control (ESC) system of modern motor vehicles is generally programmed to actively intervene to provide corrective drive control actions upon detecting a probable loss of control. When cornering, sideslip and yawing may occur if the motor vehicle has a high center of mass or is travelling at a high speed, where a large sideslip angle indicates that the motor vehicle is slipping, a large yaw rate indicates that the motor vehicle is overturning, and a small yaw rate indicates that the motor vehicle is underturning. In such circumstances, the ESC system will compare a detected current travel trace of the motor vehicle and the driver's intention, and will automatically adjust braking torque (i.e., braking intervention) and steering angle of the road wheels (i.e., steering intervention) based on a result of the comparison in an attempt to prevent an occurrence of vehicle control loss.
U.S. Pat. No. 7,143,864 discloses a concept of road wheel steering angle control with reference to a target yaw rate calculated from a detected steering wheel angle. U.S. Pat. No. 7,191,048 discloses a concept of assistive braking intervention in accordance with a detected lateral acceleration status. U.S. Pat. No. 7,584,042 discloses a concept of steering and/or braking intervention based on a compensation value obtained through performing an integration operation upon a difference between a detected yaw rate and a target yaw rate.
Nevertheless, such methods of motor vehicle stability control suffer from the drawbacks of slower response times and speed reductions due to slower hydraulic pressure buildup processes attributed to the methods of braking intervention. Furthermore, since front-wheel driven motor vehicles have center-of-gravity configurations (and hence wheel turning characteristics) different from those of rear-wheel driven motor vehicles, the aforesaid concepts of motor vehicle stability control, which rely on measurement parameters such as steering angle, vehicle speed, and vehicle load, may not be universally applied across various types of motor vehicles, especially across front-wheel driven motor vehicles and rear-wheel driven motor vehicles due to their vastly different load ratio configurations. Thus, the aforesaid methods of motor vehicle stability control have low accuracies and provide poor vehicle stabilizing effects. In addition, a yaw rate calculated based solely on a relationship between a steering wheel angle and a vehicle speed may not satisfy practical needs.